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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

A Method for Incorporating Quartz Crystal Microbalance Thermo-Gravimetric Assessment Data in Contamination Modeling

The science objectives of increasingly ambitious space missions require meeting stringent contamination requirements. Contamination transport models are based on established principles such as Fick’s law for contamination diffusion within the source material, Arrhenius factors to account for temperature variations and free molecular transport for spacecraft operating in vacuum. In addition to the science principles, empirical data obtained from ASTM E1559 testing is used for engineering contamination modeling. The ASTM E1559 test provides outgassing rate data for materials at expected spacecraft temperatures during a mission. Multiple quartz crystal microbalances (QCMs) can be operated at different temperatures to measure the amount of contamination condensation that can occur on various spacecraft surfaces. At the conclusion of the ASTM E1559 test a thermo-gravimetric assessment (TGA) can be performed by heating the QCMs at a linear rate to obtain contamination desorption data. This TGA data provides a wealth of information that can be incorporated into contamination models. A method for applying this data is presented.

Anderson, John R↗
NASA NTRS2019

In-Flight Line-Of-Sight Pointing Performance for the GOES-16 and GOES-17 Spacecraft

The Geostationary Operational Environmental Satellite-R program (GOES-R) has launched two of the next generation geostationary weather satellites, both of which are now fully operational. GOES-16 launched in November 2016, and GOES-17 launched in March 2017. In this paper, we present the pointing and pointing stability results of the two spacecraft, with specific focus on aspects of the design related to mitigating jitter. The flight instrument suite includes 6 seismic accelerometers sampled at approximately 2 kilohertz, allowing in-flight verification of pointing stability and comparison back to simulation predictions. This paper compares the observed flight results with the simulation predictions for acceleration and shock response spectrum (SRS) for various operational scenarios and instrument observation modes. Passive isolation of both the reaction wheels and the payload deck have proved to be effective in reducing jitter responses. Active Vibration Damping (AVD) of flexible-body modes attenuates the low frequency motion of the vehicle appendages, improving the low-frequency pointing performance. Knowledge of the instrument scan mirror motion is fed forward to the reaction wheel control, reducing disturbances on the spacecraft bus. Attitude knowledge and rate data are provided to the primary Earth-observing instrument with an accuracy defined by the Integrated Rate Error (IRE) requirements. The data are used to adjust instrument scanning. As we show in this paper, the in-flight performance of the GN&C (Guidance, Navigation and Control) design provides the necessary capabilities to achieve the demanding GOES-R mission objectives while its robustness enabled the simultaneous operation of the Advanced Baseline Imager (ABI) prime and redundant cryocoolers (CCs) to resolve an in-flight cooling anomaly on GOES-17.

Line-of-Sight↗
NASA NTRS1994

Some Practical Universal Noiseless Coding Techniques

Report discusses noiseless data-compression-coding algorithms, performance characteristics and practical consideration in implementation of algorithms in coding modules composed of very-large-scale integrated circuits. Report also has value as tutorial document on data-compression-coding concepts. Coding techniques and concepts in question "universal" in sense that, in principle, applicable to streams of data from variety of sources. However, discussion oriented toward compression of high-rate data generated by spaceborne sensors for lower-rate transmission back to earth.

Rice, Robert F.↗
NASA NTRS1949

Dislocation Theory of the Fatigue of Metals

A dislocation theory of fatigue failure for annealed solid solutions is presented. On the basis of this theory, an equation giving the dependence of the number of cycles for failure on the stress, the temperature, the material parameters, and the frequency is derived for uniformly stressed specimens. The equation is in quantitative agreement with the data. Inasmuch as one material parameter is indicated to be temperature-dependent and its temperature dependence is unknown, it is impossible to predict the temperature dependence of the number of cycles for failure. A predicted quantitative correlation between fatigue and creep was found to exist, which suggests the practical possibility of obtaining fatigue data for annealed solid solutions and elements from steady-state creep-rate data for these materials. As a result of this investigation, a modification of the equation for the steady-state creep rate previously developed on the basis of the dislocation theory is suggested. Additional data are required to verify completely the dislocation theory of fatigue.

Machlin, E S↗
NASA NTRS1991

Design of a communications system for multiple telemetry data channels operating simultaneously with a coherent turn-around ranging channel

This paper presents a simple technique to design a phase-modulated residual carrier communications link for optimum performance. The emphasis is on two data channels which are operated simultaneously with a ranging signal. The data channels employ PCM/PM and PCM/PSK/PM modulation schemes for high and low data rate channels, respectively. The technique proposed here selects the optimum (1) subcarrier frequency to minimize the interference between the two data channels, and (2) modulation indices for optimum balance of power between the two telemetry data channels and the coherent turn around ranging channel. The selected set of optimum modulation indices will allow for the specified bit error rate (BER) degradations in the two data channels. Although this technique is proposed to optimize the performance degradation for two data channels, generalizations can be made for more than two data channels.

Nguyen, Tien M.↗
DOE OSTI2014

Precision growth index using the clustering of cosmic structures and growth data

We use the clustering properties of Luminous Red Galaxies (LRGs) and the growth rate data provided by the various galaxy surveys in order to constrain the growth index γ) of the linear matter fluctuations. We perform a standard χ{sup 2}-minimization procedure between theoretical expectations and data, followed by a joint likelihood analysis and we find a value of γ=0.56± 0.05, perfectly consistent with the expectations of the ΛCDM model, and Ω{sub m0} =0.29± 0.01, in very good agreement with the latest Planck results. Our analysis provides significantly more stringent growth index constraints with respect to previous studies, as indicated by the fact that the corresponding uncertainty is only ∼ 0.09 γ. Finally, allowing γ to vary with redshift in two manners (Taylor expansion around z=0, and Taylor expansion around the scale factor), we find that the combined statistical analysis between our clustering and literature growth data alleviates the degeneracy and obtain more stringent constraints with respect to other recent studies.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1980

High speed lookup table approach to radiometric calibration of multispectral image data

A concept for performing radiometric correction of multispectral image data onboard a spacecraft at very high data rates is presented and demonstrated. This concept utilized a lookup table approach, implemented in hardware, to convert the raw sensor data into the desired corrected output data. The digital lookup table memory was interfaced to a microprocessor to allow the data correction function to be completely programmable. Sensor data was processed with this approach at rates equal to the access time of the lookup table memory. This concept offers flexible high speed data processing for a wide range of applications and will benefit from the continuing improvements in performance of digital memories.

Kelly, W. L., IV↗
DOE OSTI2016

A 4×8-Gbps VCSEL array driver ASIC and integration with a custom array transmitter module for the LHC front-end transmission

This paper describes the design, fabrication and experiment results of a 4×8-Gbps Vertical-Cavity Surface-Emitting Laser (VCSEL) array driver ASIC with the adjustable active-shunt peaking technique and the novel balanced output structure under the Silicon-on-Sapphire (SOS) process, and a custom array optical transmitter module, featuring a compact size of 10 mm×15 mm×5.3 mm. Both the array driver ASIC and the module have been fully tested after integration as a complete parallel transmitter. Optical eye diagram of each channel passes the eye mask at 8 Gbps/ch with adjacent channel working simultaneously with a power consumption of 150 mW/ch. As a result, the optical transmission of Bit-Error Rate (BER) less than 10E-12 is achieved at an aggregated data rate of 4×8-Gbps.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1971

Mechanism of the oxidation of titanium disilicide.

Study of the oxidation of TiSi2 at temperatures of 300 to 1300 C. Wafers prepared using the techniques of powder metallurgy had densities of 95 to 98% of the theoretical value. On oxidation at temperatures up to 600 C, the polished wafers formed a protective, titania-silica glass. The rate data indicate a complex surface and diffusion-limited mechanism. Above 600 deg C, the oxide consisted of an amorphous SiO2 film with crystalline islands of TiO2 (rutile). From 1000 to 1300 C, parabolic kinetics with an activation energy of 21.3 kcal/mole were observed. These data are consistent with a model in which the rate-determining step is the diffusion of oxygen through the silica film with the simultaneous diffusion of titanium from the substrate to the islands of rutile growing on top of the amorphous silica.

Schwettmann, F. N.↗
NASA NTRS1973

Study of information transfer optimization for communication satellites

The results are presented of a study of source coding, modulation/channel coding, and systems techniques for application to teleconferencing over high data rate digital communication satellite links. Simultaneous transmission of video, voice, data, and/or graphics is possible in various teleconferencing modes and one-way, two-way, and broadcast modes are considered. A satellite channel model including filters, limiter, a TWT, detectors, and an optimized equalizer is treated in detail. A complete analysis is presented for one set of system assumptions which exclude nonlinear gain and phase distortion in the TWT. Modulation, demodulation, and channel coding are considered, based on an additive white Gaussian noise channel model which is an idealization of an equalized channel. Source coding with emphasis on video data compression is reviewed, and the experimental facility utilized to test promising techniques is fully described.

Odenwalder, J. P.↗
NASA NTRS1973

Assuring reliability program effectiveness.

An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.

Ball, L. W.↗
NASA NTRS1974

Design of the Mariner Jupiter/Saturn 1977 telemetry system

In 1977 NASA will launch two spacecraft to perform scientific investigations of the Jupiter and Saturn planetary systems. The science payload includes a total of ten instruments to support both the interplanetary-cruise and planetary-encounter phases. These will be the first launches of a new generation of Mariner-class spacecraft designed for outer-planet missions. The telemetry-system design for these missions was especially challenging because of extreme communication ranges (1.5 billion km), high data-rate requirements (up to 115.2 kbit/sec), and more stringent data-quality requirements than previous Mariner missions. The present paper discusses the evolution and design of the Mariner Jupiter/Saturn 1977 telemetry system and presents the performance anticipated therefrom.

Wood, G. E.↗
NASA NTRS1975

ATS-6 description

Basic design features of Applications Technology Satellite-6 (ATS-6) are discussed, and a variety of experiments carried out with the satellite is described. The 9.1 m reflector is a furlable 48-rib design. The earth viewing module housing most of the electronics is connected to the reflector by an A-frame truss made of graphic fiber reinforced plastic with excellent dimensional stability over a wide temperature range. The solar arrays, extended beyond the diameter of the reflector, are fixed hemi-cylinders consisting of 16 flat panels each. The communications system is an integrated multifrequency RF repeater capable of receiving up to 3 signals in any of 4 frequency bands (C, S, L, VHF) and retransmitting them on any desired frequency in 4 frequency bands (C, S, L, UHF). Results of the Tracking and Data Relay Experiment with GEOS-3 are summarized. Accuracies of 0.1 to 0.2 deg have been maintained in the programmed mode of tracking using the ATS-6 Digital Operational Controller, and communications links for the relay of 1.56 kilobit telemetry data from GEOS and for acquisition of range and range rate data performed as predicted or better.

Redisch, W. N.↗
NASA NTRS1976

Ground data handling for LANDSAT-D

The present plans for the LANDSAT D ground data handling are described in relationship to the mission objectives and the planned spacecraft system. The end to end data system is presented with particular emphasis on the data handling plans for the new instrument, the Thematic Mapper. This instrument generates ten times the amount of data per scene as the present Multispectral Scanner, and this resulting data rate and volume are discussed as well as possible new data techniques to handle them such as image compression.

Lynch, T. J.↗
NASA NTRS1977

Ground data handling for Landsat-D

The present plans for the Landsat-D ground data handling are described in relationship to the mission objectives and the planned spacecraft system. The end-to-end data system is presented with particular emphasis on the data handling plans for the new instrument, the Thematic Mapper. This instrument generates ten times the amount of data per scene as the present Multispectral Scanner and this resulting data rate and volume are discussed as well as possible new data techniques to handle them - such as image compression.

Lynch, T. J.↗
NASA NTRS1983

Low L/D aerobrake test at Mach 10

An aerobraking Orbital transfer vehicle may be used to increase the Space Shuttle mission capability to and from high orbits. A Mach 10 wind-tunnel test was performed for a low lift-drag aerobrake, to define a preliminary aerothermal environment for this candidate concept. Test hardware simulated the ribs and stretched fabric of conceptual flight hardware. Pressures, paint-melting histories, and oilflow data were measured on the brake. Pressure and thermocouple heating rate data were measured on the payload. Brake peak heating is at the edge at all angles of attack, although the stagnation point is not outboard of 75 percent radius even at 20 degrees angle of attack. Brake ribs show slightly higher heating than flats, although pressures are essentially constant. Payload peak heating occurs near 12 degrees angle of attack, and is 30 percent of the sphere stagnation point heating (for a sphere of brake diameter). Payload pressure distributions follow the heating pattern. Reynolds number effects are small on the brake and large on the payload, for the range of test conditions: 0.4-1.0 million/foot.

Hair, L. M.↗
NASA NTRS1985

Synchronizing Heavily Encoded Data in Bad Weather

Deep space missions choose a data rate to ensure reliable communication under most conditions. Certain critical data can be more heavily encoded, to be decoded under particularly bad atmospheric conditions. It is shown that, in such a system, finding and synchronizing critical data will not be a problem.

Swanson, L.↗
NASA NTRS1986

Stratospheric photochemical studies using Nimbus 7 data. I - Ozone photochemistry. II - Development of inferred trace specie distributions

The present investigation has the objective to make use of the limb infrared monitor of the stratosphere (LIMS) data set in conducting stratospheric photochemical studies. A description of the data is provided. The data are utilized in a zero-dimensional model incorporating the relevant chemistry. The chemical reaction scheme considered is a subset of the scheme used in the Langley one-dimensional model discussed by Callis et al. (1983). Attention is given to a comparison of model results and data, a model uncertainty analysis, model response to modifications in rate data, the ozone-temperature relationship, and the diurnal variation in the upper stratospheric ozone.

Natarajan, M.↗